Pension and Other Postretirement Benefits (details) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	$ 67,000
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation	678,000
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components	(60,000)
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation	(613,000)
Defined Benefit Plan, Information about Plan Assets [Abstract]
Accrued Interest and Dividend Income	414,000	249,000
Due from broker for securities sold	321,000	448,000
Total Pension Plan Asset Receivables	735,000	697,000
Due to broker for securities purchased	839,000	42,000
Defined Benefit Plan, Fair Value of Plan Assets	215,970,000	219,014,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets, Start	219,014,000
Defined Benefit Plan, Fair Value of Plan Assets, End	215,970,000	219,014,000
General Discussion Of Pension And Other Postretirement Benefits Abstract
Aggregate Projected Benefit Obligation Qualified Plans	362,900,000	314,500,000	285,200,000
Benefit Obligations Change in Discount Rate	40,300,000	17,900,000
Benefit Obligations Change in Other Assumptions	900,000	6,500,000
Next year Regulatory Asset Amortization	15,500,000
Next year Regulatory Asset Amortization, Actuarial Losses	14,700,000
Next year Regulatory Asset Amortization, Prior Service Costs	400,000
Next year Regulatory Asset Amortization, Transition Obligations	400,000
Next year AOCI Amortization, Actuarial Losses	1,000,000
Non-Qualified Obligations	28,200,000	24,900,000	22,800,000
Health Care Cost Trend Rate Assumed for Next Fiscal Year (medical)	8.00%
Health Care Cost Trend Rate Assumed for Next Fiscal Year (drugs)	10.00%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%
Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate	2021
Range Of Pension Costs Capitalized	30 to 40 percent
Underfunded Amount of Qualified Defined Benefit Plans	146,900,000
Qualified Contributions Expected During Next Fiscal Year	28,000,000
Defined Contribution Plan, Cost Recognized	2,400,000	2,100,000	2,100,000
Multiemployer Plan Contributions	400,000	400,000	400,000
Level 3 Change In Fair Value Of Plan Assets Roll Forward [Abstract]
Level 3, Actual Return on Plan Assets	596,000
Level 3, Purchases, Sales, and Settlements	0
Level 3 Plan Assets Balance	15,317,000	14,721,000
Plan Asset Target Allocation [Abstract]
US Large Cap Equity Pension Plan Asset Target Allocation	15.00%
US Small Mid Cap Equity Pension Plan Asset Target Allocation	10.00%
Non US Equity Pension Plan Asset Target Allocation	14.50%
Emerging Markets Equity Pension Plan Asset Target Allocation	3.50%
Long Government Credit Pension Plan Asset Target Allocation	24.00%
High Yield Pension Plan Asset Target Allocation	5.00%
Emerging Market Debt Pension Plan Asset Target Allocation	5.00%
Real Estate Funds Pension Plan Asset Target Allocation	5.80%
Absolute Return Strategy Pension Plan Asset Target Allocation	12.00%
Real Return Strategy Pension Plan Asset Target Allocation	5.20%
Defined Benefit Plan Fair Value Of Plan Assets By Measurement Table [Abstract]
US Large Cap Equity Pension Assets	36,236,000	37,231,000
US Small Mid Cap Equity Pension Assets	27,310,000	27,864,000
Non US Equity Pension Assets	33,745,000	39,179,000
Emerging Markets Equity Pension Assets	10,208,000	11,476,000
Fixed Income Pension Assets	19,121,000	36,429,000
Long Government Credit Pension Assets	18,897,000
Real Estate Funds Pension Assets	15,317,000	14,721,000
Absolute Return Strategy Pension Assets	30,475,000	32,378,000
Real Return Strategy Pension Assets	15,475,000	15,452,000
Cash And Cash Equivalents Pension Assets	9,290,000	3,629,000
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Fair Value Of Plan Assets By Measurement Table [Abstract]
US Large Cap Equity Pension Assets	36,236,000	37,231,000
US Small Mid Cap Equity Pension Assets	0	0
Non US Equity Pension Assets	22,158,000	24,630,000
Emerging Markets Equity Pension Assets	10,208,000	11,476,000
Fixed Income Pension Assets	19,121,000	36,429,000
Long Government Credit Pension Assets	0
Real Estate Funds Pension Assets	0	0
Absolute Return Strategy Pension Assets	0	0
Real Return Strategy Pension Assets	15,475,000	15,452,000
Cash And Cash Equivalents Pension Assets	0	0
Total Pension Asset Investments Net Of Receivables And Payables	103,198,000	125,218,000
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Fair Value Of Plan Assets By Measurement Table [Abstract]
US Large Cap Equity Pension Assets	0	0
US Small Mid Cap Equity Pension Assets	27,310,000	27,864,000
Non US Equity Pension Assets	11,587,000	14,549,000
Emerging Markets Equity Pension Assets	0	0
Fixed Income Pension Assets	0	0
Long Government Credit Pension Assets	18,897,000
Real Estate Funds Pension Assets	0	0
Absolute Return Strategy Pension Assets	30,475,000	32,378,000
Real Return Strategy Pension Assets	0	0
Cash And Cash Equivalents Pension Assets	9,290,000	3,629,000
Total Pension Asset Investments Net Of Receivables And Payables	97,559,000	78,420,000
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Fair Value Of Plan Assets By Measurement Table [Abstract]
US Large Cap Equity Pension Assets	0	0
US Small Mid Cap Equity Pension Assets	0	0
Non US Equity Pension Assets	0	0
Emerging Markets Equity Pension Assets	0	0
Fixed Income Pension Assets	0	0
Long Government Credit Pension Assets	0
Real Estate Funds Pension Assets	15,317,000	14,721,000
Absolute Return Strategy Pension Assets	0	0
Real Return Strategy Pension Assets	0	0
Cash And Cash Equivalents Pension Assets	0	0
Total Pension Asset Investments Net Of Receivables And Payables	15,317,000	14,721,000
Pension Plans Defined Benefit [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	215,970,000	219,014,000	201,312,000
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, Start	339,338,000	307,991,000	281,127,000
Defined Benefit Plan Service Cost	7,122,000	6,688,000	6,402,000
Defined Benefit Plan Interest Cost	18,134,000	18,029,000	17,948,000
Defined Benefit Plan, Actuarial Net (Gains) Losses	44,802,000	25,275,000	23,584,000
Defined Benefit Plan, Benefits Paid	(18,269,000)	(18,645,000)	(17,149,000)
Defined Benefit Plan, Plan Amendments	0	0	(3,921,000)
Defined Benefit Plan, Benefit Obligation, End	391,127,000	339,338,000	307,991,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets, Start	219,014,000	201,312,000	163,115,000
Defined Benefit Plan, Actual Return on Plan Assets	(6,684,000)	24,651,000	28,641,000
Defined Benefit Plan, Contributions by Employer	21,909,000	11,696,000	26,705,000
Defined Benefit Plan, Benefits Paid	(18,269,000)	(18,645,000)	(17,149,000)
Defined Benefit Plan, Fair Value of Plan Assets, End	215,970,000	219,014,000	201,312,000
Defined Benefit Plan, Funded Status of Plan	(175,157,000)	(120,324,000)	(106,679,000)
Defined Benefit Plan Amounts Recognized In Regulatory Amortization And Other Comprehensive Income Net Prior Service Cost Credit Before Tax [Abstract]
Actuarial Loss (Regulatory)	10,731,000	6,740,000	6,189,000
Prior Service Costs (Regulatory)	230,000	230,000	1,260,000
Transition Obligation (Regulatory)	0	0	0
Total Regulatory Amortization In Net Periodic Benefit Costs	10,961,000	6,970,000	7,449,000
Actuarial Loss (AOCI)	854,000	707,000	449,000
Prior Service Costs (AOCI)	122,000	(43,000)	(37,000)
Total AOCI Amortization In Net Periodic Benefit Costs	976,000	664,000	412,000
Defined Benefit Plans And Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Plan Service Cost	7,122,000	6,688,000	6,402,000
Defined Benefit Plan Interest Cost	18,134,000	18,029,000	17,948,000
Defined Benefit Plan Expected Return On Plan Assets	(17,867,000)	(18,207,000)	(15,696,000)
Defined Benefit Plan Amortization Of Transition Obligations	0	0	0
Defined Benefit Plan Amortization Of Prior Service Costs	352,000	187,000	1,223,000
Defined Benefit Plan Amortization Of Net Actuarial Loss	(11,584,000)	(7,447,000)	(6,810,000)
Defined Benefit Plan Net Periodic Benefit Cost	19,325,000	14,144,000	16,687,000
Defined Benefit Plan Amount Allocated To Construction	(4,905,000)	(3,729,000)	(4,636,000)
Defined Benefit Plan Net Amount Deferred To Regulatory Balancing Account	(6,008,000)	0	0
Defined Benefit Plan Net Amount Charged To Expense	8,412,000	10,415,000	12,051,000
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Weighted Average Discount Rate (Cost)	5.49%	6.01%	6.60%
Rate of Increase in Compensation Low Range (Cost)	3.25%	3.25%	3.25%
Rate of Increase in Compensation High Range (Cost)	5.00%	5.00%	5.00%
Expected Long-Term Rate of Return (Cost)	8.25%	8.25%	8.25%
Weighted Average Discount Rate (Obligation)	4.51%	5.49%	6.01%
Rate of Increase in Compensation Low Range (Obligation)	3.25%	3.25%	3.25%
Rate of Increase in Compensation High Range (Obligation)	5.00%	5.00%	5.00%
Expected Long-Term Rate of Return (Obligation)	8.00%	8.25%	8.25%
Pension and Other Postretirement Benefit Contributions [Abstract]
Pension And Other Postretirement Benefit Contributions	22,325,000	12,088,000
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	30,109,000
Defined Benefit Plan, Benefits Paid	(18,269,000)	(18,645,000)	(17,149,000)
Defined Benefit Plan, Expected Future Benefit Payments in Year One	19,374,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	19,620,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	20,107,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	20,640,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	21,284,000
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	122,680,000
Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Defined Benefit Plan, Fair Value of Plan Assets	0	0	0
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Defined Benefit Plan, Benefit Obligation, Start	27,676,000	24,741,000	23,863,000
Defined Benefit Plan Service Cost	614,000	588,000	522,000
Defined Benefit Plan Interest Cost	1,404,000	1,436,000	1,568,000
Defined Benefit Plan, Actuarial Net (Gains) Losses	2,225,000	2,387,000	216,000
Defined Benefit Plan, Benefits Paid	(1,870,000)	(1,476,000)	(1,428,000)
Defined Benefit Plan, Plan Amendments	0	0	0
Defined Benefit Plan, Benefit Obligation, End	30,049,000	27,676,000	24,741,000
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Fair Value of Plan Assets, Start	0	0	0
Defined Benefit Plan, Actual Return on Plan Assets	0	0	0
Defined Benefit Plan, Contributions by Employer	1,870,000	1,476,000	1,428,000
Defined Benefit Plan, Benefits Paid	(1,870,000)	(1,476,000)	(1,428,000)
Defined Benefit Plan, Fair Value of Plan Assets, End	0	0	0
Defined Benefit Plan, Funded Status of Plan	(30,049,000)	(27,676,000)	(24,741,000)
Defined Benefit Plan Amounts Recognized In Regulatory Amortization And Other Comprehensive Income Net Prior Service Cost Credit Before Tax [Abstract]
Actuarial Loss (Regulatory)	289,000	131,000	17,000
Prior Service Costs (Regulatory)	197,000	197,000	197,000
Transition Obligation (Regulatory)	411,000	411,000	411,000
Total Regulatory Amortization In Net Periodic Benefit Costs	897,000	739,000	625,000
Defined Benefit Plans And Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Plan Service Cost	614,000	588,000	522,000
Defined Benefit Plan Interest Cost	1,404,000	1,436,000	1,568,000
Defined Benefit Plan Expected Return On Plan Assets	0	0	0
Defined Benefit Plan Amortization Of Transition Obligations	411,000	411,000	411,000
Defined Benefit Plan Amortization Of Prior Service Costs	197,000	197,000	197,000
Defined Benefit Plan Amortization Of Net Actuarial Loss	(289,000)	(131,000)	0
Defined Benefit Plan Net Periodic Benefit Cost	2,915,000	2,763,000	2,698,000
Defined Benefit Plan Amount Allocated To Construction	(878,000)	(904,000)	(858,000)
Defined Benefit Plan Net Amount Deferred To Regulatory Balancing Account	0	0	0
Defined Benefit Plan Net Amount Charged To Expense	2,037,000	1,859,000	1,840,000
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Weighted Average Discount Rate (Cost)	5.16%	5.78%	7.12%
Weighted Average Discount Rate (Obligation)	4.33%	5.16%	5.78%
Pension and Other Postretirement Benefit Contributions [Abstract]
Pension And Other Postretirement Benefit Contributions	1,870,000	1,476,000
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	2,056,000
Defined Benefit Plan, Benefits Paid	(1,870,000)	(1,476,000)	(1,428,000)
Defined Benefit Plan, Expected Future Benefit Payments in Year One	2,056,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	2,083,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	2,138,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	2,149,000
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	2,198,000
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 11,298,000

Absolute Return Strategy Pension Assets

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Absolute Return Strategy Pension Plan Asset Target Allocation

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No definition available.

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Cash And Cash Equivalents Pension Assets

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No definition available.

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Non-Qualified Supplemental Define Benefit Pension Obligation

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The amounts in regulatory assets related to gains and losses that are not recognized immediately and are expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented

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No definition available.

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The amounts in regulatory assets related to prior service cost or credit expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

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No definition available.

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The amounts in regulatory assets related to transition assets (obligations), origination from the adoption of FAS 87 and 106, expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

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No definition available.

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Net periodic benefit cost allocated to construction.

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The aggregate net gain (loss) recognized in regulatory amortization.

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The aggregate net prior service cost or credit recognized in regulatory amortization.

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The aggregate amount in regulatory assets expected to be recognized as a component of net periodic benefit cost over the fiscal year that follows the most recent annual statement of financial position presented, including the net gain (loss), net prior service cost or credit, and net transition asset or obligation.

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No definition available.

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Beneift obligation increase decrease due to change in discount rate

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No definition available.

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Beneift obligation increase decrease due to change in other assumtpions

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An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

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No definition available.

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Higher percentage for the range for the compensation increase for benefit obligation.

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Lower percentage for the range for the compensation increase for benefit obligation.

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Higher percentage for the range for the compensation increase for benefit cost.

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Lower percentage for the range for the compensation increase for benefit cost.

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- Definition

The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status. Prescription Drugs

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Net periodic benefit cost charged to expense.

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Net periodic benefit cost deferred to regulatory balancing account.

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No definition available.

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If aggregate disclosures are presented, the aggregate projected benefit obligation for pension plans with accumulated benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented. Qualified Plans.

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No definition available.

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- Definition

Emerging Market Debt Pension Plan Asset Target Allocation

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Emerging Markets Equity Pension Assets

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Emerging Markets Equity Pension Plan Asset Target Allocation

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Fixed Income Pension Assets

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- Definition

High Yield Pension Plan Asset Target Allocation

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No definition available.

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- Definition

The difference between fair value of level 3 plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

+ References

No definition available.

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- Definition

Level 3 Plan Assets Balance, beginning and ending

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- Definition

Purchases, sales, and settlements of level 3 plan assets that occurred during the period.

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No definition available.

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Long Government Credit Pension Assets

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Long Government Credit Pension Plan Asset Target Allocation

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The employer's best estimate, as soon as it can be reasonably determined, of qualified contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

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For qualified defined benefit pension plans, the net benefit obligation, which is the value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date offset by pension assets.

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Range of pension costs capitalized

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The net transition asset or obligation recognized, before tax, in regulatory amortization.

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Total Pension Asset Investments Net Of Receivables And Payables

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The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

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The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

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The interest rate used to adjust for the time value of money for the plan.

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1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

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The effect of a one-percentage- point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

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The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

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The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

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The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

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The amount of the aggregate benefits expected to be paid in the five fiscal years thereafter (the aggregate amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

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The amount of the benefits expected to be paid in Year 5.

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The amount of the benefits expected to be paid in Year 4.

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The amount of the benefits expected to be paid in Year 1.

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The amount of the benefits expected to be paid in Year 3.

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The amount of the benefits expected to be paid in Year 2.

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An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

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Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total.

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- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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The amount of increase or decrease due to a change in the terms of an existing plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.

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-Name Accounting Standards Codification

-Glossary Plan Amendment

-URI http://asc.fasb.org/extlink&oid=6520782

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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The ultimate trend rate for health care costs.

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The year when the ultimate health care cost trend rate is expected to be reached.

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

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Amount of contributions made to multiemployer plans for each period for which a statement of income is presented. An employer may disclose total contributions to multiemployer plans without disaggregating the amounts attributable to pension plans and other postretirement benefit plans.

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The amount of cash or cash equivalents contributed during the reporting period by the entity to fund its pension plans and its non-pension postretirement benefit plans.

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-Paragraph 28

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